For centuries, lens-based microscopy, such as light, phase-contrast, fluorescence, confocal and electron microscopy, has played an important role in the evolution of modern sciences and technologies. In 1999, a novel form of microscopy, i.e. coherent diffraction microscopy (also termed coherent diffraction imaging or lensless imaging) was developed and transformed our traditional view of microscopy, in which the diffraction pattern of a noncrystalline object or a nanocrystal is first measured and then directly phased to obtain an image. The well-known phase problem is solved by combining the oversampling method with iterative algorithms. In the first part of the talk, I will briefly describe the principle of coherent diffraction imaging. I will then present our recent experiments on coherent diffraction imaging with an X-ray free electron laser, which allows us to characterize materials at sub- 10 nm spatial resolution and sub-20 femtosecond temporal resolution.

In the second part of the talk, I will present a general method for determining 3D local structures at atomic resolution. By combining scanning transmission electron microscopy with a novel tomographic technique known as equally sloped tomography, we have imaged metallic nanoparticles at atomic resolution in three dimensions and revealed new atomic structure information that are hidden in conventional 2D projections. We expect this general method to find broad application in materials sciences, nanoscience, physics and chemistry.

1. K. S. Raines, S. Salha, R. L. Sandberg, H. Jiang, J. A. Rodríguez, B. P. Fahimian, H. C.Kapteyn, J. Du and J. Miao, “Three-dimensional structure determination from a single     view”, Nature 463, 214-217 (2010).

2. M. C. Scott, C.-C. Chen, M. Mecklenburg, C. Zhu, R. Xu, P. Ercius, U. Dahmen, B. C. Regan and J. Miao, “Electron tomography at 2.4 Å resolution”, Nature 483, 444–447     (2012).

3. C.-C. Chen, C. Zhu, E. R. White, C.-Y. Chiu, M. C. Scott, B. C. Regan, L. D. Marks, Y. Huang and J. Miao, “Three-dimensional imaging of dislocations in nanoparticles at     atomic resolution”, Nature, in press (2013).